Dynamical simulation and statistical analysis of velocity fluctuations of a turbulent flow behind a cube

A statistical approach for the treatment of turbulence data generated by computer simulations is presented. A model for compressible flows at large Reynolds numbers and low Mach numbers is used for simulating a backward-facing step airflow. A scaling analysis has justified the commonly used assumption that the internal energy transport due to turbulent velocity fluctuations and the work done by the pressure field are the only relevant mechanisms needed to model subgrid-scale flows. From the numerical simulations, the temporal series of velocities are collected for ten different positions in the flow domain, and are statistically treated. The statistical approach is based on probability averages of the flow quantities evaluated over several realizations of the simulated flow. We look at how long of a time average is necessary to obtain well-converged statistical results. For this end, we evaluate the mean-square difference between the time average and an ensemble average as the measure of convergence. This is an interesting question since the validity of the ergodic hypothesis is implicitly assumed in every turbulent flow simulation and its analysis. The ergodicity deviations from the numerical simulations are compared with theoretical predictions given by scaling arguments. A very good agreement is observed. Results for velocity fluctuations, normalized autocorrelation functions, power spectra, probability density distributions, as well as skewness and flatness coefficients are also presented

Climate change can disrupt ecological interactions in mysterious ways: Using ecological generalists to forecast community-wide effects

Ecological interactions are the backbone of biodiversity. Like individual species, interactions are threatened by drivers of biodiversity loss, among which climate change operates at a broader scale and can exacerbate the effects of land-use change, overharvesting, and invasive species. As temperature increases, we expect that some species may alter their distribution towards more amenable conditions. However, a warmer and drier climate may impose local effects on plants and animals, disrupting their interactions before noticeable changes in distribution are observed. We used a mutualistic trio from the temperate forests of South America to theoretically illustrate how climate change can disrupt ecological interactions, based on our current knowledge on this system. This study system comprises three generalist species with intersecting roles: a keystone mistletoe, a pollinator hummingbird, and a frugivorous marsupial that disperses the seeds of many species. On the one hand, drought causes water stress, increasing mortality of both mistletoe and host plants, and reducing the production of flowers and fruits. These resource shortages negatively impact animal's foraging opportunities, depleting energy reserves and compromising reproduction and survival. Finally, warmer temperatures disrupt hibernation cycles in the seed-dispersing marsupial. The combined result of these intersecting stressors depresses interaction rates and may trigger an extinction vortex if fail to adapt, with deep community-wide implications. Through negatively affecting generalist mutualists which provide resilience and stability to interaction networks, local-scale climate impacts may precipitate community-wide extinction cascades. We urge future studies to assess climate change effects on interaction networks rather than on singular species or pairwise partnerships.Fil: Fontúrbel, Francisco E.. Pontificia Universidad Católica de Valparaíso; ChileFil: Nespolo, Roberto F.. Pontificia Universidad Católica de Chile; Chile. Universidad Católica de Chile; ChileFil: Amico, Guillermo Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Watson, David M.. Charles Sturt University; Australi

Los registros más australes de Dromiciops gliroides: extendiendo su distribución más allá del bosque lluvioso valdiviano

The geographic range of a species is often limited by sampling approaches, underestimating the actual distribution. This is likely the case of Dromiciops gliroides (Microbiotheria), an endemic marsupial from southern South America. We used camera-traps to record D. gliroides for the first time in Chaitén and Futaleufú (southern Chile), expanding its known distribution 100 km to the south. Climate and forest composition in this area differs from the typical Valdivian rainforest. Activity assessments show a narrow activity patterns compared to northern populations.El rango geográfico de una especie usualmente está limitado por el muestreo, subestimando su distribución. Este sería el caso de Dromiciops gliroides (Microbiotheria), un marsupial endémico de Sudamérica austral. Usamos cámaras-trampa para registrar a D. gliroides por primera vez en Chaitén y Futaleufú (al sur de Chile), expandiendo su distribución 100 km al sur. El clima y la composición del bosque de esta área difieren del bosque valdiviano. Los patrones de actividad encontrados son más estrechos que los de las poblaciones más al norte

NuIl sex differences in General Intelligence: Evidence from the WAIS-III.

Sin resume

Heavy neutrino signals at large hadron colliders

We study the LHC discovery potential for heavy Majorana neutrino singlets in the process pp -> W+ -> l+ N -> l+ l+ jj (l=e,mu) plus its charge conjugate. With a fast detector simulation we show that backgrounds involving two like-sign charged leptons are not negligible and, moreover, they cannot be eliminated with simple sequential kinematical cuts. Using a likelihood analysis it is shown that, for heavy neutrinos coupling only to the muon, LHC has 5 sigma sensitivity for masses up to 200 GeV in the final state mu+- mu+- jj. This reduction in sensitivity, compared to previous parton-level estimates, is driven by the ~ 10^2-10^3 times larger background. Limits are also provided for e+- e+- jj and e+- mu+- jj final states, as well as for Tevatron. For heavy Dirac neutrinos the prospects are worse because backgrounds involving two opposite charge leptons are much larger. For this case, we study the observability of the lepton flavour violating signal e+- mu-+ jj. As a by-product of our analysis, heavy neutrino production has been implemented within the ALPGEN framework.Comment: Latex 36 pages, 49 PS figures. Major extension incorporating analysis for e+- e+-, e+- mu+- and e+- mu-+ final states. Final version to appear in JHE

Combined toxicity of graphite-diamond nanoparticles and thiabendazole to Daphnia magna

Carbon-based nanomaterials exhibit unique properties that make them suitable for a wide variety of industrial and biomedical applications. In this work, we studied the acute toxicity of graphite-diamond nanoparticles (GDN) combined with the fungicide thiabendazole (TBZ) to the immobilization of the cladoceran Daphnia magna in the presence and absence of the micro green algae Raphidocelis subcapitata, supplied as food source. The toxicity of GDN to D. magna decreased in the presence of R. subcapitata, while that of TBZ increased, the latter suggesting a carrier effect to TBZ. GDN-TBZ mixtures were fitted to the most common conceptual models applied to mixture toxicity: Concentration Addition (CA), Independent Action (IA) and Combination Index (CI). For GDN-TBZ mixtures in the absence of food the best fit was obtained with dose ratio deviation from CA model, while in the presence of food, dose level deviation from CA gave a better fit. The binary mixtures of GDN and TBZ showed synergistic toxic interactions at low concentrations, which could be attributed to the increased bioavailability of TBZ adsorbed on GDN. For higher concentrations of GDN, the binary mixtures turned antagonistic due to particle agglomeration. Our study provides evidence that deviations from additivity are dose dependent and relevant for the risk assessment of mixtures of nanoparticles with other chemical pollutants.publishe

Plataformas de sensado basadas en nanopartículas monometálicas y aleaciones

El objetivo general del plan de tesis es la síntesis, caracterización y aplicación de nanopartículas (NPs) metálicas protegidas con grupos orgánicos. Nuestro enfoque está en el estudio de los comportamientos físico-químicos de tales sistemas y el aprovechamiento de los mismos para la construcción de sensores de gas, principalmente en la detección de H2, así como también la posibilidad de volcar la plataforma de sensado a aplicaciones en catálisis. En esta etapa de la investigación se ensayaron distintas rutas de síntesis para la obtención de distintas nanopartículas aleadas (Pd-Au; Ag-Pd) en medio acuoso. El método de síntesis consiste en la obtención de nanopartículas protegidas por citrato por reducción de un precursor metálico con NaBH4 en presencia de Citrato de sodio (CitNa3) en medio acuoso, estas nanopartículas (5-10 nm)  pueden luego ser crecidas (20-40 nm). Con el fin de obtener estructuras core-shell, las nanopartículas crecidas son sometidas a intercambio galvánico utilizando un precursor metálico adecuado (Ej: Pdº NPs/AuCl4- ; Agº NPs/PdCl4=). Con el fin de obtener nanopartículas dispersas en medio orgánico (tolueno) se realizaron ensayos de transferencia interfacial (tolueno/agua) con octilamina (C8H17-NH2), este grupo orgánico no solo protege al core metálico (mono metálico o aleado) sino que además permite la transferencia de las nanopartículas en medio acuoso a medio no polar. Tanto los ensayos de intercambio galvánico como los ensayos de trasferencia de fase fueron seguidos por espectroscopia UV-vis, se pudo constatar el intercambio galvánico en el sistema Pdº NPs/AuCl4-  por la desaparición de los picos de absorción correspondientes al AuCl4-, la aparición de picos de absorción asignables a especies de PdCl4=  y la aparición de una banda de absorción alrededor de los 500 nm asignable al plasmón de Auº. En el sistema Agº NPs/ PdCl4= el intercambio galvánico fue evidenciado por la disminución en la intensidad del plasmon de Agº centrada en los 400 nm y la ausencia de los picos de absorción del PdCl4=.Facultad de Ciencias Exacta

Plataformas de sensado basadas en nanopartículas monometálicas y aleaciones

El objetivo general del plan de tesis es la síntesis, caracterización y aplicación de nanopartículas (NPs) metálicas protegidas con grupos orgánicos. Nuestro enfoque está en el estudio de los comportamientos físico-químicos de tales sistemas y el aprovechamiento de los mismos para la construcción de sensores de gas, principalmente en la detección de H2, así como también la posibilidad de volcar la plataforma de sensado a aplicaciones en catálisis. En esta etapa de la investigación se ensayaron distintas rutas de síntesis para la obtención de distintas nanopartículas aleadas (Pd-Au; Ag-Pd) en medio acuoso. El método de síntesis consiste en la obtención de nanopartículas protegidas por citrato por reducción de un precursor metálico con NaBH4 en presencia de Citrato de sodio (CitNa3) en medio acuoso, estas nanopartículas (5-10 nm)  pueden luego ser crecidas (20-40 nm). Con el fin de obtener estructuras core-shell, las nanopartículas crecidas son sometidas a intercambio galvánico utilizando un precursor metálico adecuado (Ej: Pdº NPs/AuCl4- ; Agº NPs/PdCl4=). Con el fin de obtener nanopartículas dispersas en medio orgánico (tolueno) se realizaron ensayos de transferencia interfacial (tolueno/agua) con octilamina (C8H17-NH2), este grupo orgánico no solo protege al core metálico (mono metálico o aleado) sino que además permite la transferencia de las nanopartículas en medio acuoso a medio no polar. Tanto los ensayos de intercambio galvánico como los ensayos de trasferencia de fase fueron seguidos por espectroscopia UV-vis, se pudo constatar el intercambio galvánico en el sistema Pdº NPs/AuCl4-  por la desaparición de los picos de absorción correspondientes al AuCl4-, la aparición de picos de absorción asignables a especies de PdCl4=  y la aparición de una banda de absorción alrededor de los 500 nm asignable al plasmón de Auº. En el sistema Agº NPs/ PdCl4= el intercambio galvánico fue evidenciado por la disminución en la intensidad del plasmon de Agº centrada en los 400 nm y la ausencia de los picos de absorción del PdCl4=.Facultad de Ciencias Exacta

PICCOLO White-Light and Narrow-Band Imaging Colonoscopic Dataset: A Performance Comparative of Models and Datasets

Colorectal cancer is one of the world leading death causes. Fortunately, an early diagnosis allows for e_ective treatment, increasing the survival rate. Deep learning techniques have shown their utility for increasing the adenoma detection rate at colonoscopy, but a dataset is usually required so the model can automatically learn features that characterize the polyps. In this work, we present the PICCOLO dataset, that comprises 3433 manually annotated images (2131 white-light images 1302 narrow-band images), originated from 76 lesions from 40 patients, which are distributed into training (2203), validation (897) and test (333) sets assuring patient independence between sets. Furthermore, clinical metadata are also provided for each lesion. Four di_erent models, obtained by combining two backbones and two encoder–decoder architectures, are trained with the PICCOLO dataset and other two publicly available datasets for comparison. Results are provided for the test set of each dataset. Models trained with the PICCOLO dataset have a better generalization capacity, as they perform more uniformly along test sets of all datasets, rather than obtaining the best results for its own test set. This dataset is available at the website of the Basque Biobank, so it is expected that it will contribute to the further development of deep learning methods for polyp detection, localisation and classification, which would eventually result in a better and earlier diagnosis of colorectal cancer, hence improving patient outcomes.This work was partially supported by PICCOLO project. This project has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 732111. Furthermore, this publication has also been partially supported by GR18199 from Consejería de Economía, Ciencia y Agenda Digital of Junta de Extremadura (co-funded by European Regional Development Fund–ERDF. “A way to make Europe”/ “Investing in your future”. This work has been performed by the ICTS “NANBIOSIS” at the Jesús Usón Minimally Invasive Surgery Centre